Showing papers on "Packed bed published in 1982"

Stripping of carbon dioxide from monoethanolamine solutions in a packed column

Abstract: A procedure using only fundamental physico-chemical data is developed for the design and analysis of packed columns used for solvent recovery in gas purification processes involving chemical reaction. The results of 173 experiments on the mass transfer performance of a pilot-scale regenerator stripping CO2 from loaded monoethanolamine solutions are reported and compared with model predictions. Anomolous responses of the overall mass transfer coefficient to changes in process conditions are observed and explained by the process model which is found to predict correctly both the magnitude of the coefficient and its response.

Hydrodynamic properties of pulses in two-phase downflow operated packed columns

Abstract: In a packed column with downward cocurrent two-phase flow, under certain circumstances pulsing flow can be observed. Several properties of these pulses were determined: pulse frequency, pulse velocity, liquid holdup in a pulse, liquid holdup outside the pulses and the pulse height. These parameters were measured as functions of gas and liquid flow rate, column diameter and packing diameter. All experiments were carried out with a water/ air system. It was found that the pulse frequency is completely governed by the real liquid velocity in excess of a critical liquid velocity at the pulsing onset. The relationship is worked out in terms of flow rates and is then shown to correlate pulse frequencies for several systems; data from the literature are also included. Pulse velocity is shown to be completely determined by the real gas velocity in the bed. The ratio between the maximum liquid holdup at the front of apulse and the liquid holdup between pulses is found to be nearly constant at a value of 1.6. Finally, the pulse height is practically independent of gas and liquid flow rates, tending to be slightly higher in a system with larger packing particles.

Optimal design of packed bed cells for high conversion

Abstract: In connection with the electrochemical purification of metal containing waste waters, the realization of a high concentration decrease per pass is one of the goals of design optimization. For a packed bed cell with crossed current and electrolyte flow directions high conversion in conjunction with a large space time yield requires limiting current conditions for the whole electrode. For establishing the concentration profiles in the direction of flow a plug flow model is used. These considerations result in a new packed bed electrode geometry for which an analytical bed depth function is derived. The basic engineering equations of such packed bed electrodes are given, and design equations for different arrangements are developed. The reliability of this scaling-up method is shown by comparison of theoretically predicted and experimental performance data of two cells. Engineering aspects such as easy matching of cells to waste water properties and parametric sensitivity are discussed. Some technical applications are reported.

Packed column thermal reactor for an analytical instrument

Abstract: straight elongated column (42) intended to be used as the reactor in an analytical instrument. The column (42) contains an inert packing material for obtaining the flow path length required for a fluid stream entering the reactor. The adjustments (58) are incorporated in the ends of the column (42) so that their width does not exceed the width of the column (42). The column configuration (42) for a reactor allows for greater flexibility in the choice of temperature control mechanisms used to heat and cool the reactor.

Method for gasoline yield enhancement in the fixed bed methanol-to-gasoline process

Abstract: Gasoline product yield is enhanced in a fixed bed methanol-to-gasoline process by splitting the conversion reactor into a series of smaller conversion reactors such that the total amount of catalyst normally present in the single conversion reactor is present in equal quantities in the smaller conversion reactors. The smaller conversion reactors operate sequentially with the next conversion reactor beginning operation only when the preceeding conversion reactor is catalytically exhausted. The by-passing of one or more of the catalyst beds prevents premature deactivation of the catalyst beds downstream of the point at which the reaction products are removed.

Mobil methanol-to-gasoline process

Abstract: This paper explains that 2 major concerns in the development of the methanol-to-gasoline (MTG) process are heat removal from the reactor and the formation of durene (1-,2-,4-,5-tetramethylbenzene). Conversion of methanol to gasoline is highly exothermic (about 1510-1740 kJ/kg of methanol converted) and the adiabatic temperature rise would be almost 600C. Within Mobil, 2 types of reactor configurations were adopted for development: an adiabatic fixed-bed and a fluid-bed reactor. The fixed-bed reactor is ready for immediate commercialization and is more suitable for smaller scale operation. The fluid-bed reactor is under development and possesses the following potential advantages over the fixed-bed reactor: reaction heat removal is simplified by using the superior heat transfer characteristics of a fluid bed; when coupled with alkylation, the fluid bed gives a higher gasoline yield than the fixed bed; and constant catalyst activity, gasoline selectivity, and gasoline quality can be maintained with the fluid-bed operation. Fixed-bed is cyclic.

Carbon dioxide removal method employing packed solid calcium hydroxide

Abstract: In order to remove carbon dioxide from an off-gas stream and immobilize it in solid stable form, the gas is passed through a packed bed of calcium hydroxide maintained at a temperature in the range 10° C.-50° C., the moisture content of the gas being controlled so as to correspond to a relative humidity from 40% to 100% at the bed temperature.

Current paths and electrolysis efficiency in bipolar packed-bed electrodes

Abstract: The characteristics of bipolar packed-bed electrodes were studied by using copper deposition reaction from a copper sulfate solution. Ferrite pellets were used as a particulate phase and were packed in three kinds of mode. The Faradaic current in the particulate phase, the by-pass current in the electrolyte phase and the short-circuiting current were measured separately. The minimum bipolar cell voltage was a function of decomposition voltage, distance between two plate electrodes, pellet diameter, and solid holdup. For regularly packed bipolar electrodes, the interaction between Faradaic and by-pass current was small, and a simplified parallel current model is proposed. For randomly packed bipolar electrodes, the interaction was not negligible at higher cell voltages. The minimum value of energy consumption was observed at a particular cell voltage which was a function of pellet size and packing mode. Because of increase in the short-circuiting current due to copper deposition, the energy consumption in the randomly packed bed increased with increase in electrolysis time. The regularly packed bed where the direction of current was parallel to the plain faces of the pellets was found to be the most efficient under the present experimental conditions.

Liquid chromatographic separation of hydrocarbons

Abstract: There is disclosed a method for the separation and identification of components contained in hydrocarbon mixtures, such as paraffins, olefins, napthenes and/or aromatics, by liquid chromatography by use of a chromatographic column packed with a microparticulate material having a pore size of less than about 500 Å and possessing aromaticity, preferably polystyrene/divinyl benzene having a pore size of less than about 100 Å, the microparticulate material being slurry packed in a solvent medium. The hydrocarbon mixture is passed through the packed column using a mobile phase comprising a solvent having a solvent strength parameter, e°, of less than about 0.1 such as a C5 to C8 alkane; and the paraffins, olefins, napthenes, and/or aromatics are separately eluted and identified. Also disclosed is an apparatus for the characterization and separation of paraffins, olefins, napthenes, and aromatics contained in hydrocarbon mixtures, the apparatus comprising: a chromatographic column packed with a microparticulate material having a pore size of less than about 500 Å and possessing aromaticity, and slurry packed in a solvent medium; an injector for injecting a sample of the hydrocarbon mixture into said column; a solvent reservoir and pump to provide a mobile phase to the column comprising a solvent having a solvent strength parameter, e°, of less than about 0.1 such as a C5 to C8 alkane; and a detector to detect and identify the paraffins, olefins, napthenes, and aromatics as they are eluted from the column.

Dynamic studies of dispersion and channeling in fixed beds

Abstract: An experimental and theoretical study was carried out to relate the extent of channeling in a packed column to the response in the effluent gas to a tracer input. When the response curve showed a distinct peak associated with a channel, it was possible to establish the flow rate and void area of the channel from only the response curve. The experimental data provided new information on Peclet numbers in packed columns with nonuniform void fractions (low tube-to-particle diameter ratios).

Adsorption separation apparatus

Abstract: A method for separating a starting fluid containing at least one component which is easy to adsorb and at least one component which is hard to adsorb into the respective components by the use of an adsorption separator which comprises a packed bed where an adsorbent for such components is packed and a fluid passage connecting the front and rear ends of said packed bed so that the fluid is able to be circulated, the method comprising the first step of feeding the starting fluid to an intermediate portion of the packed bed while withdrawing from the separator a fluid rich with either of the components in an amount equal to the feed of the starting fluid from a position downstream of the feed port, the second step of stopping the feed of the fluid to and the withdrawal of the fluid from the separator and moving the fluid remaining in the separator toward the downward direction, and the third step of feeding a desorbent fluid to the separator and simultaneously withdrawing from the separator a fluid rich with either of the components in an amount equal to the feed of the desorbent fluid from a position downstream of the desorbent feed port, the respective withdrawals of fluid from the separator being conducted at least two different positions, the adsorption bands being left in part of the packed bed in the third step. Apparatus for carrying out the method is disclosed.

Operational characteristics of anaerobic packed-bed reactors

Abstract: Laboratory and full-scale tests have shown that the operational characteristics of anaerobic packed-bed ractors are closely related to the physical design features of the reactor. The chemical oxygen demand (COD) removal efficiency seems to be inversely related to the upflow velocity through the void spaces within the media matrix. This means that the type and size of media are important factors in design but the efficiency does not seem to be related directly to either unit surface area or to porosity. While all operating characteristics have not been evaluated in depth and all design parameters have not been developed fully, anaerobic packed-bed reactors should be considered seriously as a method for converting a wide range of organic industrial wastes to methane gas. 7 figures, 1 table.

Processing of hydrocarbons in fixed catalyst bed with redistribution means

Abstract: Hydrocarbons are processed in a co-current flow packed catalyst bed reactor containing one or more redistribution means, e.g., redistribution screens, in the packed catalyst bed. If more than one redistribution means are used, they are spaced within the bed of catalyst over a predetermined distance. Optionally, the surface area of the redistribution means is less than the cross-sectional surface area of the reactor bed to allow for packing of a relatively smaller size solid particles, as compared to the rest of the catalyst in the bed, in the area between the edge of the redistribution means and the inner wall of the reactor means. The use of the redistribution means prevents channeling of the reactants near the reactor wall region, and assures uniform distribution of the reactants throughout the packed catalyst bed. The invention is applicable to relatively low velocity systems operating at liquid linear velocity of 0.3 cm/sec. or less.

Design of a Packed Bed Thermal Storage Unit for a Solar System

Abstract: A method for the design and sizing of a packed bed thermal storage unit for a hot air solar heating system is presented. A controlled bypass of the heat storage unit during the retrieval process is used in order to maintain the fluid temperature leaving the system at a constant value. The use of a bypass arrangement with a closed air circulation loop for the collector enables the storage unit to operate at a higher mean temperature and the system to utilize the maximum allowable pressure drop. This results in a greater heat storage per unit volume of storage material. The complete solar system is simulated numerically during both the heating and retrieval modes of operation to obtain a set of design charts for sizing the thermal storage unit. In the simulation, consideration is given to geographical location, composition of the storage bed and the maximum allowable pressure drop across the bed. A set of design curves for State College, Pennsylvania, is presented.

A packed-bed balance reactor for gas adsorption and gas-solid reactions under elevated pressures

Abstract: A packed-bed balance reactor (PBBR) is presented as a novel and relatively low-cost alternative to a microbalance for use in adsorption experiments and gas-solid reactions under elevated pressures. The apparatus consists of a packed-bed flow reactor placed, together with the inlet and outlet connections, on a commercially available electronic balance. This construction combines the advantages of a microbalance (direct weight measurement) with those of a packed-bed flow reactor (elevated pressure conditions, larger sample size and less severe external mass transfer limitations under flow conditions). The gas flow rate through the reactor does not affect the weight read-out, whereas the pressure dependency is caused by the amount of gas present in the reactor. The operating principle is demonstrated by CO2 adsorption on activated charcoal under flow conditions and by gasification of activated charcoal with CO2. Specific surface areas, calculated from adsorption isotherms, correspond well with those obtained from a conventional volumetric method. Gasification reaction rates based on the weight decrease equal those calculated from the gas flow rate and the product gas analysis.

Effect of compaction on conversions in immobilized enzyme packed columns.

Abstract: Effect of compaction on behavior of immobilized enzyme packed bed reactor is investigated by the use of invertase entrapped by polyacrylamide gel. Void fraction decreases with increase of superficial velocity. Also, apparent reaction rate decreases extraordinarily. This phenomenon is explained by decrease of surface area of immobilized enzyme particles. The ratio of surface area to volume of particles is found to be five times smaller than for spherical particles in the extreme case.

Monte Carlo simulation of radiant transport through an adiabatic packed bed or porous solid

Abstract: Computations are presented that can be exploited to yield effective view factors for the transmission of radiation through porous solids or packed beds. The approach is valid only to the extent that there is equivalence between gas molecule behavior in the Knudsen diffusion and photon behavior in the case of radiant transport. This imposes the following restrictions: the pore size or bed interstices should be sufficiently small that they can be considered optically thin yet much larger than the wavelength of the radiation; the pore walls or packing surface must be diffuse surfaces so that reflected or emitted photons leave at random angles to the normal with a cosine probability distribution; the pore walls or packing surface must be adiabatic surfaces; and the porous solid is large compared to the pores (or the packed bed large compared to the packing). Included are diagrams of a porous plug (or packed bed) separating a source of radiation from a sink and possible trajectories of incident radiation; a graph of fraction of photons transmitted through the plug as a function of plug thickness; and correlation of ''data'' from the Monte Carlo simulations with the porosity, pore size and standard deviation of pore sizemore » for several solids.« less